Rotary heat treating oven



Oct. 28, 1969 J. L. KEMMERER, JR., ET AL ROTARY HEAT TREATING OVEN Filed Jan. 4, 1965 Fig.l.

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John L. KemmonnJr. 8 Eduard G. Buschw Oct 28, 1969 J. L. KEMMERER, JR., ETAI- 3,475,286

ROTARY HEAT TREATING OVEN 3 Sheets-Sheet 2 Filed Jan. 4, 1965 uw Rro mnu/f mmu/ Vm m M G Lm nw h l u fm A 4 3 U uw O'l'lnllll'l Oct. 28, 1969 J. L. KEMMERER, JR.. ETA'- 3,475,286

ROTARY HEAT TREATING OVEN Filed Jan. 4, 1965 3 sheets-sheet s INVENTOFB John L,Kemmercr,Jr. a d Edward G. Buschow l Ma@ -yaygh rug;

United States Patent O U.S. Cl. 202-117 7 Claims ABSTRACT F THE DISCLOSURE A method and apparatus for continuously treating noncaking coal and other discrete materials of low non-agglutinating-values, consisting in delivering the materials onto a rotating hearth in a heated oven chamber, the hearth sloping from its outer periphery at the point of admission of materials thereinto to its center at which a soaking'pit is provided, a plurality of stationary rabbles being disposed above the hearth, progressively advancing the materials to the soaking pit. The rabbles are shaped and disposed to insure thorough stirring and positive advance of the material on the hearth surface from the outer periphery theretof to a centrally located point of discharge of the treated materials.

This invention relates generally to a method and apparatus for the continuous coking, devolatilizing and/or calcining of carbonaceous materials such as the so-called non-caking coals (coals which have a low agglutinating value). anthracite coal, wood products, green petroleum coke, pellets or briquettes containing controlled percentages of bituminous coking coal and other carbonaceous materials or inerts either with or without a bituminous binder. It also relates to the calcining of dolomite, limestone and cement rock, the reclaiming of calcium oxide from carbonate sludge, the decomposition of carbonates, sulphates and chlorides, the reactivation of activated carbon, and the like.

Heretofore the devolatilizing and calcining above mentioned has normally and generally been done in operations of 4a batch type. For example, a common method of making coke isl in the well known vertical shaft coke oven. There are numerous coals that cannot be properly coked by conventional methods and apparatus or if coked in the conventional way yield poor and unsatisfactory products. For example, the coking of bituminous Western coals in conventional apparatus yields a notoriously poor product in that the residual volatiles in the product are too high and often unacceptable. This product also lacks uniformity in that volatiles will be driven off to a lesser degree in some portions of the batch than in other portions.

The calcining of green petroleum coke is normally performed in a rotary kiln. The rotation of the kiln tends to degradate the coke particles and a portion of the finer material is blown out the stack with the products of combustion. Furthermore, segregation occurs within the bed of material with the result that the larger particles move freely on the surface and the iines remain in the middle of the bed. This causes the larger particles to be more thoroughly devolatilized than the smaller material.

Batch calcining operations with limestone similarly have shortcomings with regard to uniformity in that it generally produces a dead-burned lime which has a hard shell on the outside of the product pieces that inhibits its ability to slake.

We have invented a method and apparatus for the treatmentof such materials that has overcome these problems, which yields a more even and uniform product and for example yields an excellent coke product from bituminous 3,475,286 Patented Oct. 28, 1969 ice western coals having retained volatiles of only from .5 to 1.5 ZJ, and in treating limestone yields a soft-burned lime which is a desirable product in that it slakes much easier than dead-burned lime.

We provide a method of continuously treating so-called non-caking coal, limestone and other materials of low or non-agglutinating values comprising the steps of continuously delivering the material to be treated onto a hearth in a heated oven chamber adjacent the outer periphery thereof to form a bed thereon, relatively moving the hearth and the material thereon with respect to a plurality of rabbles disposed above the hearth and spaced progressively outwardly from the center thereof, progressively advancing the material toward a material outlet at the center of the hearth by disposing said rabbles such that they eX- tend into the bed at an angle of attack that moves the bed progressively inwardly toward said material outlet, turning said bed over and over during its progressive movement toward the material outlet, and discharging the treated material into the material outlet at the center of the hearth.

In a preferred method of treating such materials, the material is delivered onto a generally circular hearth and the hearth and the material thereon are rotated in opposition to said plurality of rabbles which are stationarily disposed above the hearth. The material is discharged into a soaking pit at the center of the hearth and the treated material is then discharged from the bottom of the soak- 1ng pit.

In an apparatus for carrying out our method we provide an oven comprising means constituting la heated chamber, a hearth in the chamber, a material outlet at the center lof the hearth, means for delivering material to the hearth adjacent the outer periphery thereof to form a bed of material on the hearth, rabbles disposed above the hearth and means for relatively moving the hearth and rabbles, the rabbles being spaced progressively outwardly from the center of the hearth and disposed to move material on the hearth progressively inwardly toward the material outlet upon relative movement between the hearth and the rabbles, the outward spacing between the rabbles progressively increasing inwardly of the hearth to compensate for decrease in the dimensions of the portions of the hearth opposed to the respective rabbles whereby to maintain substantially constant the depth of the bed of material on the hearth.

In la preferred embodiment of the invention we provide a generally circular hearth with a soaking pit at the center thereof and means for rotating the hearth and the material thereon in opposition to the rabbles which are stationarily mounted above the hearth, said soaking pit having discharge means at the bottom thereof.

Preferably the rabbles are so mounted as to be independently adjustable in their disposition with respect to the hearth and the material thereon so that they may be varied as conditions demand.

Also we preferably provide a hearth which is downwardly inclined toward the center from its outer periphery to promote movement of the bed as it is progressively advanced toward the material outlet. It is apparent that by so inclining the hearth a gravity assist takes place in moving the bed inwardly that also promotes stirring or mixing the bed.

To further promote turning over of the bed we also may provide rabbles that are plow-shaped.

In instances where relatively high temperatures are contemplated in utilizing our apparatus, we preferably provide means for cooling the rabbles such as by circulating coolant therewithin.

In another preferred embodiment of our apparatus, we provide a hearth that is stepped progressively downwardly toward the center from the outer periphery to promote the turning over of the bed as it is advanced toward the material outlet.

In still another preferred embodiment we provide rabbles that are staged such that there is a leading rabble and a following rabble at substantially each spacing of the rabbles, each said following rabble extending deeper into the bed than its respective leading rabble whereby said bed is advanced progressively inwardly in stages with the upper portion of the bed being progressively advanced prior to the lower portion of the bed to promote a turning over of the bed as it progresses toward the material outlet.

Other details, objects and advantages of the invention will become apparent as the following description of certain present preferred embodiments thereof and certain present preferred methods of practicing the same proceeds.

In the accompanying drawings we have shown certain present preferred embodiments of the invention and have illustrated certain present preferred methods of practicing the same in which FIGURE 1 is a vertical section through a furnace embodying our invention;

FIGURE 2 is an enlarged fragmentary view of the rabbles and rabble holding means of FIGURE 1;

FIGURE 3 is a section on the line III-III of FIG- URE 2;

FIGURE 4 is a section on the line IV-IV of FIG- URE 2;

FIGURE 5 is a fragmentary section on the line V-V of FIGURE 3;

FIGURE 6 is an enlarged view partly in section of a pair of rabbles according to our invention;

FIGURE 7 is a section on the line VII- VII of FIG- URE 6;

FIGURE 8 is a fragmentary section of hearth and plows according to a second embodiment of our invention;

FIGURE 9 is a section at 90 to FIGURE 8 taken on the line IX--IX of FIGURE 10; and

FIGURE 10 is a fragmentary plan view of the hearth of FIGURES 8 and 9.

Referring to the drawings we have illustrated a furnace according to our invention having a rotary hearth 10 with an inner hearth surface 11 sloping from the outer periphery downwardly to a central axially extending soaking pit 12 integral with and depending from the hearth 10. The rotary hearth 10 is suported on spaced rollers 13 mounted on a furnace frame 14 and is driven by a motor and a rack and pinion drive in conventional manner for rotary hearth furnaces. A curb 15 extends vertically above the hearth surface 11 at its outer periphery and carries a trough 16 with sand 17. A liquid may be used instead of sand, if preferred.

The furnace frame 14 carries roof beams 20 which support a refractory roof 21 having a central flue 22. The roof 21 has a depending wall 23 carrying ange 24 which extends into the sand 17 carried in trough 16 forming a rotary sand seal between the roof 21 and hearth 10. The roof 21 is provided with air ports 25 receiving air from duct 26 mounted on the furnace frame 14. 'Ille ports 25 direct air downwardly towards the hearth. Sidewalls 23 of the roof are provided with ports 27 receiving air from duct 28 also mounted on the frame 14. The ports 27 direct air generally across the hearth in a radial direction. Burners 29 are provided in the roof to bring the furnace to operating temperature and to provide additional heat for those reactions which are not or not completely autogenetic. A feed chute 30 passes through the roof 21 adjacent the sidewall 23 and is provided with a vertically adjustable delivery end 31 extending to a point adjustably selected to deliver a selected thickness of feed onto hearth surface 11. A radially extending U- shaped rabble pit 32 is formed in the roof from the flue 22 to the roof wall 23. The bottom of the pit 32 is provided with slots 33 adapted to slidably receive rabbles 34. Rabbles 34 may be solid or of hollow plate-like structure with inner vertical bafiies 35, depending upon the temperature involved. For the higher temperatures, of course, the latter is lpreferred. Each baffle is provided with inlet 36 and outlet 37 coolant conduits which also act as supports for the rabbles. Coolant such as water or air s delivered to the inlet 36 and into rabble 34 on one side of the bafe 35 and then under baffle 35 to the opposite side of the rabble and out through outlet pipe 37. Refractory seals 38 are provided on conduits 36 and 37 to tit within slot 33. The conduits 36 and 37 are held between two angular rabble holders 39 and 40 which are held together by bolts 41. The rabble holders 39 and 40 are fastened between adjustable carrier angle beams 42 and 43 by bolts 44. Vertical adjustment screws 45 are provided at each end of each adjustable carrier beam 42 and 43. These screws 45 bear on fixed rabble beams 46 and 47 which extend across the rabble pit 32 as shown in FIGURE 3.

A rotary discharge table 50 is provided beneath the soaking pit 12 to receive the output of such pit. A fixed discharge spout or plow 51 is mounted in frame 14 between the soaking pit 12 and discharge table 50. The spout 51 is provided with a peripheral trough 52 carrying sand 53 into which a depending flange 54 on the soaking pit extends to form a sand seal.

The operation of the furnace described above is as follows. The burners 29 are fired to bring the furnace up to the desired temperature which depends upon the nature of the material being devolatilized or calcned. Material to be devolatilized or calcined is fed through feed chute 30 and is continuously spread to the desired thickness and width along the outer periphery of hearth surface 11. As the hearth rotates the material encounters the rabbles 34. Each set of rabbles deflects material striking it into the next adjacent concentric ring of the sloping hearth surface so that the flow of material from the periphery of the hearth surface 11 to the soaking pit 12 is generally in spiral concentric rings, each of greater width so that as the rings become smaller the area `becomes greater providing a uniform depth. These concentric spiral rings are diagrammatically illustrated in FIGURE 4 together with the relative position of each rabble with respect to such rings. The vertical position of the rabbles determines the residual amount of material which is to be left on each ring as the hearth rotates. The rabbles tend to cause mixing and inversion of the bed several times as the material moves downwardly from the hearth periphery to the soaking pit. This permits more uniform heating and reaction and provides a more uniform product and is an important attribute of this invention.

In the embodiment of our invention illustrated in FIGURES 8 through 10 we have illustrated a stepped or terraced hearth configuration 60 in which each concentric ring is defined by a vertical surface 61 so that the hearth surface 60 is in a series of steps rather than sloped or inclined hearth surface 11 of FIGURES 1 through 7. We have also illustrated a modified rabble arrangement in which the rabbles are arranged one 70 preceding another 71. The tirst rabble 70 is higher than second or following rabble 71 so as to remove a top layer from the step and discharge it first to the next lower step and then by the second rabble remove a next lower layer which becomes the top of the next succeeding ring. In this way several desirable immersions and stirring of the material is assured. It will be understood that the paired rabble arrangement just described applies as well to other ernbodiments of our invention.

While we have 4shown fiat quadrangular rabbles in the illustrated embodiments, it is possible to have various configurations of rabbles such for example as one having a configuration similar to that of a conventional mold board plow design to turn the material plowed from the concentric ring.

In the foregoing specilication we have illustrated and described certain presently preferred embodiments of our invention, it will be understood, however, that this invention may be otherwise embodied within the scope of the following claims.

We claim:

1. A heat treating oven comprising a circular heated chamber having a vertical axis including a roof structure therefor, an inclined hearth in said chamber, burner means in said chamber to bring the oven to operating temperatures to remove volatile components from materials undergoing treatment therein, a material outlet at the center of said hearth, an outlet for volatile materials, means for delivering materials to the hearth adjacent the outer periphery thereof to form a bed of material on said hearth, stationary rabbles mounted in said roof and disposed above the said hearth, means for rotating said hearth about the axis relative to said stationary rbbles, said rabbles being spaced progressing outwardly from the center of said hearth and arranged to move material on said hearth progressively inwardly toward the matreial outlet upon relative movement between the hearth and said rabbles, the spacing between said rabbles progressing outwardly from the center of the hearth to the periphery progressively decreasing to compensate for an increase in the radial dimensions of the portions of the hearth opposed to the respective rabbles whereby to maintain substantially constant the depth of the bed of material on the hearth.

2. An oven as claimed in claim 1 wherein said hearth is downwardly inclined in the direction from its outer periphery inwardly toward the material outlet to promote movement of the bed as it is progressively advanced toward said material outlet.

3. An oven as claimed in claim 1 wherein said rabbles are staged such that there is a leading rabble and a following rabble at substantially each progressively outwardly spaced location of the rabbles, each said following rabble extending deeper into the bed than its respective leading rabble whereby at each respective location of said staged rabbles said bed is advanced progressively inwardly in stages with the upper portion of the bed being progressively advanced prior to the lower portion of the bed to promote a turning over of the bed as it progresses toward the material outlet.

4. A heat treating oven comprising means constituting a circular heated chamber having a vertical axis and including a roof portion therefor, a generally circular inclined hearth in the chamber, burner means in said chamber to bring the oven to operating temperatures to recover volatile components from the materials undergoing treat- -ment therein, means for rotating the hearth about the axis, a material outlet at the center of the hearth, an outlet for volatile materials, means for delivering materials to the hearth adjacent the outer periphery thereof to form a bed of material on the hearth and rabbles stationarily mounted in said roof portion of said chamber, said rabbles being spaced progressing outwardly from the center of the hearth and disposed to move material on the hearth progressively inwardly toward the material outlet upon rotation of the hearth, the spacing of the rabbles progressing outwardly from the center of the hearth to the periphery progressively decreasing to compensate for an increase in the radial dimension of the portions of the hearth opposed to the respective rabbles whereby to maintain substantially constant the depth of the bed of material on the hearth.

5. A11 oven as claimed in claim 4 wherein said rab- -bles are staged such that there is a leading rabble and a following rabble at substantially each progressively outwardly spaced location of the rabbles, each said following rabble extending deeper into the bed than its respective leading rabble whereby at each respective location of said staged rabbles said bed is advanced progressively inwardly in stages with the upper portion of the bed being progressively advanced prior to the lower portion of the bed to promote a turning over of the bed as it progresses toward the material outlet.

6. A heat treating oven comprising means constituting a heated chamber including a roof structure therefor, a generally circular inclined hearth in the chamber, said chamber having a vertical axis, means for rotating the hearth about the axis, burner means in said chamber to bring the oven to operating temperatures to recover volatile components from the materials undergoing treatment therein, a material outlet at the center of the hearth, an outlet for volatile materials, means for delivering material to the hearth adjacent the outer periphery thereof to form a bed of material on the hearth and rabbles stationarily mounted in said roof above the hearth, the rabbles being spaced progressing outwardly from the center of the hearth and disposed to move material on the hearth progressively inwardly toward the material outlet upon rotation of the hearth, the spacing of the rabbles progressing outwardly from the center of the hearth to the periphery progressively decreasing to compensate for an increase in the diameter of the portions of the hearth opposed to the respective rabbles whereby to maintain substantially constant the depth of the bed of material on the hearth, the hearth being sloped progressively downwardly in the direction from its outer periphery inwardly toward the material outlet to promote a turning over of the bed as it progresses toward the material outlet.

7. A11 oven as claimed in claim 6 wherein said rabbles are staged such that there is a leading rabble and a following rabble at substantially each progressively outwardly spaced location of the rabbles, each said following rabble extending deeper into the bed than its respective leading rabble whereby at each respective location of said staged rabbles said bed is advanced progressively inwardly in stages with the upper portion of the bed being progressively advanced prior to the lower portion of the bed to promote a turning over of the bed as it progresses toward the material outlet.

References Cited UNITED STATES PATENTS 985,053 2/1911 Noad 202-117 XR 2,676,006 4/ 1954 Martin 263-26 1,878,581 9/1932 Ab-Der-Halden 202-104 NORMAN YUDKOFF, Primary Examiner D. EDWARDS, Assistant Examiner U.S. Cl. X.R. 

